I chose not to mention my SO rep (73k. and #5 on the all time C++ users list) a week ago, when I applied for a job.
It seemed tacky and desperate. If the employer isn't very familiar with StackOverflow, I don't think mentioning an artificial score on a Q&A website is going to make a good impression. I know I would personally consider it a negative if i was doing the hiring, and the candidate kept trying to draw attention to his user profile on an arbitrary website that means nothing to me. It's a risk I don't want to take.
I was just invited to an interview, and there, depending on circumstances, I may mention it, if he asks me something where it would be relevant.
We'll see how it goes. ;)